1. Field of the Invention
The present invention relates to a low-cost, easy-to-use, and efficient method for manufacturing a semiconductor device, which eliminates the need for the formation or removal of barrier metals upon formation of bumps, and to a high-performance semiconductor device with fine bumps arranged at a narrow pitch.
2. Description of the Related Art
Attempts have been made in recent years to achieve downsizing of semiconductor devices and greater packaging density, with the trend moving toward for thinner, smaller electronic devices. Against this background, the trend towards finer electrode pitch in a semiconductor device has created a new demand to achieve fine pitch bump—nowadays, for example, pillar-shaped electrodes (bumps) have been used suitably. Now, an example of a conventional semiconductor device is shown in FIG. 9.
In the semiconductor device shown in FIG. 9, equally spaced electrode pads 510 are formed on one surface of a semiconductor substrate 500, and a cover film 520 is formed thereon in such a way as to cover the space between each of the electrode pads 510. A protective film 530 runs on the semiconductor substrate 500 in such a way as to cover the entire surface of the cover film 520, including a part of each electrode pad 510. Solder bumps 550 are formed on the electrode pads 510, with barrier metals 540 being interposed between them. The barrier metal 540 has a function of increasing the adhesion between the electrode pad 510 and the solder bump 550.
In such an external terminal configuration it is required that the barrier metals 540 be also miniaturized, with a reduction in bump pitch. This miniaturization is, however, difficult to achieve and results in undesirable cost increase. Moreover, when such solder bumps are used, they become nearly spherical in a reflow process, making it difficult to achieve finer bump pitch. Note in such a conventional semiconductor device that bumps can be formed at a pitch of about 170 μm to 220 μm.
There are some proposed methods that can be adopted for the formation of the bumps: A method that provides openings around electrodes formed on a covered circuit board and embeds solder, which has been supplied to the circuit board under reduced pressure, in the openings by use of a squeegee (see Japanese Patent Application Laid-Open (JP-A) No. 2004-128354); and a method that prints solder paste under reduced pressure onto a printed wiring board having solder pads (see Japanese Patent Application Laid-Open (JP-A) No. 2002-111192). Bumps formed with these methods, however, have a problem that bump pitch is not narrow enough, because they are formed of solder and thus become spherical in a reflow process.
In addition, there is a known method that utilizes electroplating for the formation of bumps. With this method, a barrier metal is generally formed between a bump and an interconnection (or pad). Such a barrier metal has an advantage that it increases the adhesion between the bump and pad and functions as a common electrode upon formation of the bump on the pad by electroplating. The trend moving toward for finer bump pitch has been requiring miniaturization of barrier metals; however, this is difficult to achieve and results in undesirable cost increase, running counter to the tendency to reduce the cost per semiconductor device and package.
Moreover, the following has also been proposed as a bump formation method: A barrier metal formation process is omitted by forming an antireflection film, which is made of the same material as a barrier metal, on the surface of a pad, and the antireflection film is then used as a common electrode during electroplating for the formation of bumps (see Japanese Patent Application Laid-Open (JP-A) No. 8-162456). With this method, however, an unnecessary interconnection layer is exposed to the outside after the formation of bumps, which needs to be removed. For this reason, a process similar to a conventional barrier removal process is required, and this method is not satisfactory in terms of the simplification of the manufacturing process.
Accordingly, a low-cost, easy-to-use, and efficient method for manufacturing a semiconductor device, which eliminates the need for the formation or removal of barrier metals upon formation of bumps and which can form bumps at a narrow pitch, and a high-performance semiconductor device with fine bumps arranged at a narrow pitch have yet been provided.
It is an object of the present invention to solve the foregoing conventional problems and to achieve the objects described below. Specifically, it is an object of the present invention to provide a low-cost, easy-to-use, and efficient method for manufacturing a semiconductor device, which eliminates the need for the formation or removal of barrier metals upon formation of bumps, and to a high-performance semiconductor device with fine bumps arranged at a narrow pitch.